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Friday, June 29, 2012

'Science' without Falsification

Bryan Caplan is tired of being sneered at by "high-status academic economists":

The Curious Ethos of the Academic/Appointee, by Bryan Caplan: High-status academic economists often look down on economists who engage in blogging and punditry. Their view: If you can't "definitively prove" your claims, you should remain silent. 

At the same time, though, high-status academic economists often receive top political appointments. Part of their job is to stand behind the administration's party line. They don't merely make claims they can't definitively prove; to keep their positions, appointees have to make claims they don't even believe! Yet high-status academic economists are proud to accept these jobs - and their colleagues admire them for doing so. ...

Noah Smith has something to say about "definitive proof":

"Science" without falsification is no science, by Noah Smith: Simon Wren-Lewis notes that although plenty of new macroeconomics has been added in response to the recent crisis/depression, nothing has been thrown out...

Four years after a huge deflationary shock with no apparent shock to technology, asset-pricing papers and labor search papers and international finance papers and even some business-cycle papers continue to use models in which business cycles are driven by technology shocks. No theory seems to have been thrown out. And these are young economists writing these papers, so it's not a generational effect. ...

If smart people don't agree, it may because they are waiting for new evidence or because they don't understand each other's math. But if enough time passes and people are still having the same arguments they had a hundred years ago - as is exactly the case in macro today - then we have to conclude that very little is being accomplished in the field. The creation of new theories does not represent scientific progress until it is matched by the rejection of failed alternative theories.

The root problem here is that macroeconomics seems to have no commonly agreed-upon criteria for falsification of hypotheses. Time-series data - in other words, watching history go by and trying to pick out recurring patterns - does not seem to be persuasive enough to kill any existing theory. Nobody seems to believe in cross-country regressions. And there are basically no macro experiments. ...

So as things stand, macro is mostly a "science" without falsification. In other words, it is barely a science at all. Microeconomists know this. The educated public knows this. And that is why the prestige of the macro field is falling. The solution is for macroeconomists to A) admit their ignorance more often (see this Mankiw article and this Cochrane article for good examples of how to do this), and B) search for better ways to falsify macro theories in a convincing way.

I have a slightly different take on this. From a column last summer:

What Caused the Financial Crisis? Don’t Ask An Economist, by Mark Thoma: What caused the financial crisis that is still reverberating through the global economy? Last week’s 4th Nobel Laureate Meeting in Lindau, Germany – a meeting that brings Nobel laureates in economics together with several hundred young economists from all over the world – illustrates how little agreement there is on the answer to this important question.
Surprisingly, the financial crisis did not receive much attention at the conference. Many of the sessions on macroeconomics and finance didn’t mention it at all, and when it was finally discussed, the reasons cited for the financial meltdown were all over the map.
It was the banks, the Fed, too much regulation, too little regulation, Fannie and Freddie, moral hazard from too-big-to-fail banks, bad and intentionally misleading accounting, irrational exuberance, faulty models, and the ratings agencies. In addition, factors I view as important contributors to the crisis, such as the conditions that allowed troublesome runs on the shadow banking system after regulators let Lehman fail, were hardly mentioned.
Macroeconomic models have not fared well in recent years – the models didn’t predict the financial crisis and gave little guidance to policymakers, and I was anxious to hear the laureates discuss what macroeconomists need to do to fix them. So I found the lack of consensus on what caused the crisis distressing. If the very best economists in the profession cannot come to anything close to agreement about why the crisis happened almost four years after the recession began, how can we possibly address the problems? ...
How can some of the best economists in the profession come to such different conclusions? A big part of the problem is that macroeconomists have not settled on a single model of the economy, and the various models often deliver very different, contradictory advice on how to solve economic problems. The basic problem is that economics is not an experimental science. We use historical data rather than experimental data, and it’s possible to construct more than one model that explains the historical data equally well. Time and more data may allow us to settle on a particular model someday – as new data arrives it may favor one model over the other – but as long as this problem is present, macroeconomists will continue to hold opposing views and give conflicting advice.
This problem is not just of concern to macroeconomists; it has contributed to the dysfunction we are seeing in Washington as well. When Republicans need to find support for policies such as deregulation, they can enlist prominent economists – Nobel laureates perhaps – to back them up. Similarly, when Democrats need support for proposals to increase regulation, they can also count noted economists in their camp. If economists were largely unified, it would be harder for differences in Congress to persist, but unfortunately such unanimity is not generally present.
This divide in the profession also increases the possibility that the public will be sold false or misleading ideas intended to promote an ideological or political agenda.  If the experts disagree, how is the public supposed to know what to believe? They often don’t have the expertise to analyze policy initiatives on their own, so they rely on experts to help them. But when the experts disagree at such a fundamental level, the public can no longer trust what it hears, and that leaves it vulnerable to people peddling all sorts of crazy ideas.
When the recession began, I had high hopes that it would help us to sort between competing macroeconomic models. As noted above, it's difficult to choose one model over another because the models do equally well at explaining the past. But this recession is so unlike any event for which there is existing data that it pushes the models into new territory that tests their explanatory power (macroeconomic data does not exist prior to 1947 in most cases, so it does not include the Great Depression). But, disappointingly, even though I believe the data point clearly toward models that emphasize the demand side rather than the supply side as the source of our problems, the crisis has not propelled us toward a particular class of models as would be expected in a data-driven, scientific discipline. Instead, the two sides have dug in their heels and the differences – many of which have been aired in public – have become larger and more contentious than ever.

Finally, on the usefulness of microeconomic models for macroeconomists -- what is known as microfoundations -- see here: The Macroeconomic Foundations of Microeconomics.

Update: See here too: Why Economists Can't Agree, another column of mine from the past, and also Simon Wren-Lewis: What microeconomists think about macroeconomics.

    Posted by on Friday, June 29, 2012 at 07:20 AM in Economics, Macroeconomics, Methodology, Weblogs | Permalink  Comments (54)

          


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